1. Field of the Invention
The present invention relates to a method of manufacturing friction members such as brakes and clutch facings, and more particularly, to a method of treating a back plate after a friction material is attached thereto and prior to a painting process.
2. Description of the Related Art
Friction members such as pads for disk brakes, brake shoes and clutch facings are formed by attaching a friction material to a back plate made of ferrous material.
Relative movement added to the friction member pressed with a disk rotor or an opposing clutch plate, and frictional force generated at that moment causes an automobile to be stopped or to be transmitted driving force of an engine to wheels. As a result, considerably large shearing force is generated between the friction material and the back plate. Therefore, strong adhesive force between the friction material and the back plate to bear the shearing force has been required.
FIG. 2 is a flow chart showing a conventional method of manufacturing a friction member. At first, a steel plate as a material is punched out through pressing to form a back plate (#100). A large amount of oil for rust prevention or lubrication is adhered to the work punched out as described above. The oil may reduce adhesive force when a friction material is attached, so that it is washed out with water containing several percent of alkali degreasing agent (#102).
Then, grinding particles are blasted in a shot-blasting process to remove oxide films and burrs at pressing, and the surface of the work is made rough until ten point height of roughness profile (Rz) becomes approximately several micrometers (#104), which allows adhesive area to be increased to improve adhesive strength. In addition, since rust or oxide films on the adhesive face may reduce the adhesive force, the rust and oxide films are removed in the sandblasting process when the face is made rough.
It is also possible to simultaneously perform the degreasing and shot-blasting by adding alkali-degreasing agent to slurry in a wet shot-blasting process.
The back plate, which is made rough, and form which rust, oxide films and the like thereon are removed in the above-mentioned process, is treated with a solution for phosphate coating to form a film of zinc phosphate, zinc phosphate calcium, or the like with the thickness of 3 to 5 xcexcm on the surface thereof (#106). This film functions together with a primer layer described below to prevent rust. The film is inorganic and the primer layer is organic, so that they cooperate to improve effect on rust prevention.
In order to form a primer layer on the surface of the back plate, firstly, liquid phenol resin diluted with alcohol is applied to the back plate, and then the back plate is fed to a furnace to dry and harden the resin (#108).
Next, a bonding agent is applied to the primer layer (#109), and a friction material is mounted to the layer. Then, the friction material is pressed and heated by a press so as to be attached to the back plate (#110). The friction material is made from mixture of a bonding material, a fiber material and a filling material. As the bonding material, thermosetting resin such as phenol resin and urea resin are used. As the fiber material, organic fiber such as aramid fiber, inorganic fiber such as glass fiber and metal fiber such as stainless steel fiber are adopted. As the filling material, organic powder such as powder obtained by grinding tier rubber, metal pieces or powder made from copper alloy, aluminum, zinc or the like, and inorganic powder or particle such as graphite powder are used. In order to attach the friction material to the back plate, two methods are known. In one method, powder material is preliminarily formed in advance and is pressed to a back plate with heat added to bind the powder material and the back plate with each other. In the other method, powder material itself is mounted to a back plate, and they are pressed with each other while they are heated to bind with each other. In the present invention, any method is available.
After that, the back plate is painted to prevent rust and improve appearance (#112), and excessive painting material stick to the friction face is removed by grinding (#114) to obtain a friction member.
However, in the above manufacturing method, in the pressing process in which a friction material is attached to a back plate, release agent is attached to the back plate; a friction material, which is pressed and heated, melts and is forced out from a clearance between the back plate and a mold; the friction material is caught when the mold is closed; or a part of the friction material scatters before hardened and is attached to the back plate and hardened thereon, which causes dirty things or undesirable matters to stick to the back plate. In addition, in each process, the friction material and the back plate as a work collide with each other, or the work strikes against a wall of a container accommodating the work, which may produce bruises. Further, at the heating, a coating may deteriorate. These may cause problems such as uneven and floating painting films.
The present invention has been made to solve the above problems and to provide a method of manufacturing a friction member with high painting performance in which undesirable matters, which stick to the frictional member before painting, are removed, and degreasing and recovery of damaged portions are carried out.
To accomplish the above objective, a method of manufacturing a friction member according to the present invention is characterized in that the method comprises the steps of: attaching a friction material to a back plate; treating the back plate with the friction material prior to painting process; and painting at least the back plate.
In the above method, the treating prior to painting process may be shot-blasting, and with this shot-blasting, a surface of the back plate is made rough up to 5 to 50 xcexcm in ten point height of roughness profile (Rz). In addition, the treating prior to painting process can be coating with phosphate.
Further, in the above method, the treating prior to painting process may be shot-blasting and coating with phosphate after the shot-blasting; after the painting, a friction face of the friction material can be ground; and the painting may be painting with powder coating, and prior to the painting, a friction face of the friction material can be ground.